PubMed Health⌕ Search

Biomedical subjects

T E Fischer

Publications and source records attributed to T E Fischer.

14 recordsLinked to original sources
PubMed1980

Bond strength of bimaterial acrylic resin combinations.

While further research is necessary on the subject of the strength and nature of the bond between different types of acrylic resins, our study shows that specimens fabricated from heat-accelerated BPM showed considerably higher transverse strength values when compared with the various bimaterial combinations. From this, and from the fact that all bimaterial combinations broke at the joining interface, it can be inferred that none of the acrylic resin bimaterial combinations developed a true "chemical bond."

Acrylic Resins↗
PubMed1979

Evaluation of sunlight stability of polyurethane elastomers for maxillofacial use. II.

The effect of selected UV stabilizers on the stability of mechanical properties of a polyurethane material, Calthane ND2300, was evaluated. The addition of UV stabilizers prolonged the service life of the systems studied but did not achieve completely satisfactory results. The tensile strength and modulus of elasticity decreased after extended exposure to UV. The rate of decrease, however, was much less for the specimens with UV stabilizers. The polyurethane system that contains a mixture of a UV stabilizer and an antioxidant is considered to be the best of the groups tested, in terms of the percentage of retention of tensile strength and modulus of elasticity. It was also found that elongation at break was increased when the duration of UV aging was increased. This phenomenon occurred in all the systems, with or without UV stabilizers, and can be understood in terms of the concepts of the fragmentation of macromolecules that resulted from UV aging. The physical appearance in conjunction with mechanical property tests are needed to ensure the successful performance of any UV stabilizer.

Chemical Phenomena↗
PubMed1978

Evaluation of sunlight stability of polyurethane elastomers for maxillofacial use. I.

The evaluation of the efficiency of polymer additives with special emphasis on uv absorbers and antioxidants in polyurethane elastomers has been completed. Aliphatic polyurethanes were chosen for this study because their properties closely relate to the requirements of maxillofacial prosthesis. The polyurethane elastomers were either synthesized by ourselves or formulated according to the manufacturer's recommendation. Eleven different types of uv absorbes, coupled with one antioxidant, were incorporated into the polyurethane systems. The Atlas twin-lamp carbon arc Weatherometer was used as the source of uv. The samples were periodically withdrawn for examination of yellowing and tackiness. It was found that, although the incorporation of uv stabilizers enhanced the uv resistance of polyurethanes, the problem of tackiness resulting from uv aging was not solved satisfactorily. The phenomenon of yellowing, however, was significantly improved, mainly due to the aliphatic structure of polyurethanes. The most promising uv absorbers are Tinuvin 770 and the combination of Tinuvin 328, ZnO, and an antioxidant. Their effectiveness in other polyurethane systems is not known and further research is underway to explore this field. Hopefully, these findings will greatly assist the successful application polyurethane elastomers in maxillofacial prosthesis.

Biocompatible Materials↗